Torqmatic 900-T Hellcat Transmission
Transmission (Hydra-Matic) Division of General
Motors Corporation in World War Two / WWII
1939-1962 as Detroit Transmission Division
1962-1990 as Hydra-Matic Division
Combined with GM engine Divisions as Powertrain in 1990
This page updated 12-27-2016.
Abstract: Even though Detroit Transmission
developed what became one of GM's most recognizable products in the
Hydra-Matic and later Turbo Hydra-Matic transmission, its name has been
lost to history. In 1962 the name of the
Division changed to Hydra-Matic, which is the name most persons familiar
with the auto industry recognize. In 1990 Hydra-Matic was absorbed into GM
Powertrain and was no longer an independent Division of GM. During
WWII Detroit Transmission developed Hydra-Matic and Torqmatic
transmissions that introduced the automatic transmission to American
tanks. Tank automatic transmissions designed by GM Research and
Detroit Transmission Division late in WWII have been standard equipment
on American tanks ever since the end of the war.
The complete story is
below, including Detroit Transmission's 1944 wartime era booklet
entitled "Teamwork in Peace and War".
A state of the art WWII technology leader?
It may be hard to believe 70 years later that the M5 light tank, like
this forlorn example in downtown Hartford City, IN, was a technology
leader in WWII. While the 37mm gun was insufficient to destroy
another tank, and its armor plate too thin to protect the crew against
German tank guns, its Hydra-Matic transmission was state of the art.
Every tank or tank destroyer built for the US military after the M5, including the M1 Abrams,
had an automatic transmission. Detroit Transmission is responsible
for this technical revolution, starting with the early technology of the Hydra-Matic and Torqmatic
transmissions. Author's photo
How the Hydra-Matic came to be named
When Detroit Transmission
was created, the Hydra-Matic transmission had not yet been developed,
and it had not yet been named. When the development of the
transmission utilized the hydraulic fluid that was in the hydraulic
coupling to also flow through the body and valves of the transmission
itself, it was named Hydra-Matic. This stood for the hydraulic fluid that flowed
through it, and for the fact that it now automatically shifted through
the gears without any assistance from the driver.
A General History of
Detroit Transmission Division
Division of General Motors began in 1939 for the production of the new shiftless
transmission now known as Hydra-Matic for introduction in the 1940
Oldsmobile. The following year, Cadillac introduced it on its
vehicles. When automobile production stopped in February of 1942 for
the duration of World War Two,
200,000 transmissions had been shipped to Olds and Cadillac.
During the war Hydra-Matics were used in various tanks and armored
continued to increase sales after the war, as drivers switched from manual shifting to
the ease of automatic shifting. On September 22nd, 1947 Detroit
Transmission shipped its 500,000th Hydra-Matic.
This 1940 Oldsmobile chassis and drive
train is on display at the Ypsilanti Automobile Heritage Museum in
Ypsilanti, MI. The significance of this 1940 Olds is
that it was part of the first year introduction of the Hydra-Matic
transmission, the first fully automatic transmission to be offered for
sale. Author's photo.
The development of the automatic
transmission prompted the forming of the Detroit Transmission Division by
GM management to manufacture the units. Author's photo.
General Motors policy was, and still may be,
for one car division to introduce a new product for sale rather than all
of them. This allows the corporation to monitor acceptance by the
public, and confine any issues that arise to one particular
division. In the case of the Hydra-Matic, the rough shifting issues
did not prevent excellent acceptance by the public, and the introduction
of the product at Cadillac for the 1941 model year. Author's photo
at the Ypsilanti Automobile Heritage Museum.
The Detroit Transmission Plant moved into
this existing six story factory on Riopelle Street in Detroit, MI on May 15, 1939.
Originally the Division
occupied 99,416 square feet on the bottom three floors. It
moved to the fourth floor at the end of 1940; and into
the fifth floor in 1941. This gave the Division a total of 275,698 square feet. By March
1943 all six floors were in use and floor space was at 623,403 square
feet; dedicated to the manufacture of the Hydra-Matic transmission.
When Torqmatic went into production, manufacturing was set up in a
building across the street.
The Livonia Plant Fire
After WWII the
Division moved from its original location on Riopelle Street in Detroit
to a 34.5 acre plant in Livonia, MI. The Livonia plant was the
scene of the August 12th, 1953 fire that destroyed the plant and shut
down production of Hydra-Matics for twelve weeks. Not only were
Cadillac and Oldsmobile Divisions affected but Pontiac, Nash, Hudson,
Kaiser and Lincoln were also offering the Hydra-Matic as an option on
their vehicles During this period new
equipment was made by all GM divisions, which had all tool rooms working
seven days a week, twelve hours a day. Simultaneously, Detroit Transmission moved
into the former Ford Willow Run bomber plant, and made Hydra-Matics
vacated by GM in 2010 during the Great US Automobile Industry Meltdown.
When I went worked Plant Protection for Lansing Fisher Body on while working my way through
college in the late sixties, the Detroit Transmission Division fire was
still discussed. This event
dictated much of what we did at Fisher Body. As a result of the fire,
started by sparks from a welder igniting nearby flammable liquids, GM
implemented standard policy which still requires on-location approval by a Plant Protection fire
inspector before any welding or cutting is done. Fire prevention
within GM was driven by the Livonia fire. When I arrived at
Delco-Remy and became a supervisor in one of many tool rooms, I heard
stories from the "old timers" about working 7 days a week, 12 hours a
day remaking the tooling to restart Hydra-Matic production. All GM
tool rooms were involved in this massive tooling endeavor.
An aerial photo of the infamous Detroit
Transmission fire in Livonia, MI on August 12, 1953.
In 1962 Detroit Transmission Division became
the Hydra-Matic Division of GM.
Besides making millions of transmissions, Hydra-Matic built
469,217 M16A1 rifles that the military desperately needed for the
Vietnam war. The author's M16A1, that he was issued by the
Michigan National Guard in 1971, was built by Hydra-Matic.
Author's photo added 12-24-2015.
In 1990 Hydra-Matic Division of GM, as it was
then known, was merged into GM Powertrain and lost its individuality and
World War Two
Detroit Transmission won the Army-Navy "E" for
Excellence Award on June 22, 1944. It then added a star six months
This was earned for the always meeting schedule for its Hydra-Matic and
Torqmatic transmissions utilized in US Army tanks and tank destroyers.
Detroit Transmission Division
World War Two / WWII Production Numbers
/ Statistics: Detroit Transmission Division of GM produced 54,991
Hydra-Matic and Torqmatic transmissions for tanks, tank destroyers, and
armored cars during World War Two. The Division also produced Browning machine guns parts
for the 1,218,837 weapons that four other GM divisions built during the
The Hydra-Matic Transmission in World War
Two: The Detroit Transmission Hydra-Matic was the most utilized
automatic transmission in armored vehicles during WWII. Along with
the Detroit Transmission Torqmatic also used in armored vehicles, they
were the only two of their type used. The Hydra-Matic was also the
first of its type to be used by the military in tanks and armored cars.
Initial use of a Detroit Transmission Division
was on May 29, 1939 when a Detroit Diesel Division powered M2 tank had a
heavy duty four speed transmission installed in it. This was the
first time an automatic transmission was installed in a tank. The
advantages were immediately clear to the military ordnance officers:
elimination of engine stalling as the fluid coupler did not mechanically
lock up the engine to the transmission, full power could used under all
conditions, elimination of the heavy shift lever, best of all, the
elimination of the clutch and the double clutching required every time
the driver had to change gears. By eliminating the clutch and
manual shifting of gears, the driver was able to concentrate on looking
where the tank was going and not being distracted with manipulating the
gears and clutch.
Manual transmissions in tanks also had the
severe disadvantage of slowing down on the battlefield when changing
gears, making them easier targets to be hit by enemy fire. The new
automatic transmission eliminated this tactical disadvantage.
In February 1941 a newer, heavier duty five
speed transmission was installed in the M2 tank, which was now heavier
with added armor and weapons. The one engine was having problems
moving the tank. According to page 18 in "Teamwork in Peace and
War", it was Detroit Transmission engineers that suggested the use of
two Cadillac V-8 engines matched with two Hydra-Matic transmissions that
resulted in the M5 Stuart tank.
If one refers to "Cadillac...From Peace to
War" on the Cadillac page of this website, that Division notes that it
broached the subject of a new light tank with two of its engines and
Hydra-Matic transmissions to Army Ordnance. Which version is
correct? Most likely both, as no doubt both Divisions were working
with the Ordnance Department on projects to improve the tank by the use
of their products.
The first run of the new M5 Stuart tank with
the new Hydra-Matic 250-T transmission took place on September 17, 1941
at the General Motors Proving Grounds in Milford, MI. Next the new
tank went on a 560 cross country trip on public roads from Detroit to
the Aberdeen Proving Grounds in Maryland. Drivers on the trip were
able to easily negotiate the hills of Pittsburgh in with no driver
fatigue. The dawn of a new era of tanks transmissions had arrived.
After more successful testing at the Aberdeen Proving Grounds the Army
ordered the first 266 M5 Stuarts, the first of 1,824 M5s and a total of
24,941 light tanks, armored cars and landing vehicle tanks equipped with
the Hydra-Matic transmission during WWII.
An aside: One can only wonder
what civilians thought of the M5 as it drove through cities and towns
across the eastern US in late 1941. The author remembers a similar
type incident in the Castleton area of Indianapolis after 9-11-2001.
Allison Transmission was doing engineering development on a GM of Canada
LAV, and took it out on the local streets for a test run. Paranoid
civilians thought the country was under attack because one armored
vehicle was driving around and called the police. Needless to say,
Allison did not do any more road tests in the area. Were the
civilians in 1941 were as paranoid as those in 2002?
For the complete inside story of the
development of the Hydra-Matic not only military use in WWII, the the
early work for Oldsmobile and Cadillac, please read pages 1 through 25
of "Teamwork in Peace and War" at the bottom of this page.
The Torqmatic Transmission in World War
It should be noted that current historic literature sometimes spells
the transmission name Toquematic. This is incorrect. Please
see the 1944 Detroit Transmission booklet below entitled "Teamwork in
Peace and War" for verification of the proper spelling; Torqmatic.
Development of the Torqmatic began in December 1942 and on February
17, 1943 it was placed on a dynameter for testing. More testing
then took place on several different heavy vehicles at the Milford
The Torqmatic transmission was similar to the
Hydra-Matic with the exception that it used a "Hydraulic Torque
Converter" instead of the fluid coupling used in the Hydra-Matic.
While similar in function, the torque converter has a stator
that decreases slippage at low rpms, just what was needed to get tanks
moving from a stop in a hurry. This was the first application of a
torque converter in an automatic transmission. After World War Two,
Detroit Transmission would incorporate the more costly and complex
technology into its Hydra-Matics, and the term Torqmatic would disappear
from use. But the torque converter has been a staple of automatic
transmissions for 50 years.
Detroit Transmission opened a second plant
across the street from its original facility for the manufacture of the
Torqmatic transmission, which was used in 2,507 Buick built M18 Hellcat
tank destroyers. This had three forward gears and one for reverse.
It was mated to a Continental R-976-C2 nine cylinder radial aircraft
engine that produced 400 hp at 2,400 rpms. This was four times the
horsepower that the Hydra-Matic 250-T saw in the Cadillac V-8 engine.
Not only was this the first use of the Detroit Transmission Torqmatic
transmission, it was the first use of a torque converter and the
matching of an automatic transmission to an aircraft radial engine.
The second and final Torqmatic transmission
went into the T26E3/M26 Pershing built at the end of the war. The
Perishing was powered by 500hp Ford V-8 engine, which was 20% more
horsepower than the radial engine in the 18 ton M18 Hellcat.
The M26 Pershing weighed in at 46 tons. Therefore the Torqmatic
for this tank had to be considerably larger and more capable than the
one for the Hellcat. The Torqmatic with very little slippage at low
rpms was key to getting and keeping the heavy tank moving with
what was found to be an underpowered engine for its weight.
The first application of the Torqmatic.
The M18 Hellcat tank destroyer matched the Detroit Transmission
Torqmatic automatic three forward speed transmission with an R-975 radial
aircraft engine that produced up to 400 hp. This was four times
the horsepower of the Cadillac V-8, resulting in the need for a
much more capable transmission than the Hydra-Matic 250-T for the M5. This was also the only time an
automatic transmission was matched with an aircraft radial engine.
This M18 Hellcat is at the Ropkey Armor Museum. Author's photo
Looking through the driver's hatch the
Detroit Transmission Division of GM Torqmatic automatic transmission is
viewable. The Buick M18 was the only tank destroyer to have an
automatic transmission. Author's photo added 12-27-2016.
Here the gearshift handle is viewable along
with the gear indication on top of the transmission. On the floor
there are only the accelerator and brake pedals. A clutch pedal is
not needed with the automatic transmission. Author's photo.Author's photo
Author's photo added 12-27-2016.
This view through the open assistant
driver's hatch lets one look at the Detroit Transmission Division of GM
built Torqmatic transmission. The M18 and the M24 were the last
American tank destroyers or tanks to have power applied to the front of
the tracks, and have the transmission located between the driver and
assistant driver. Author's photo added 12-25-2015.
Transmission Division of GM World War Two Applications
M5 Stuart tanks
M5A1 Stuart tanks
M8 3 inch howitzer motor carriages
M24 Chaffee tanks
Staghound Armored Cars
Mark 1 Armored Snowmobile
| T18E2 Boarhounds
M18 Tank Destroyers
M26 Pershing tanks
The Legacy of the Detroit Transmission
Hydra-Matic and Torqmatic Tank Transmissions: During the later
part of WWII, Army Ordnance, GM Research, and Detroit Transmission
developed Cross Drive Transmission which was completed in 1945.
The transmission was designated the CD-850, and Allison built it in
Indianapolis, IN after the war for use in the M46, M47, M48, and M60
tanks. Allison then developed the next generation tank
transmission that is currently used in the M1 Abrams main battle tank.
In 1946 General Motors made an internal
technology transfer. Allison Division of General Motors, which had
exclusively produced inline aircraft engines, such as the V-1710 used in
the P-38 Lightning, was tasked by the Corporation with making heavy duty
transmissions for not only tanks, but commercial vehicles such as trucks
and buses. Detroit Transmission was then allowed to focus on the
larger market of automotive passenger car applications using the trade
Today Allison no longer produces aircraft
engines as that product line was purchased by Rolls-Royce. Allison
Transmission is also no longer part of General Motors, but is the
largest producer of heavy duty transmissions in the world. Since Allison Transmissions
took over the heavy duty transmission business in 1946, its transmission
for trucks and buses carry the trade name Torqmatic.
Unfortunately, Allison Transmission does not
acknowledge the pioneering engineering work done by Detroit Transmission
and others during WWII previous to the 1946 technology transfer.
In its history portion of its website it shows in 1946 it developed the
CD-850 tank transmission. Technology this complicated just did not appear out of thin air as is
implied on the website. It is unfortunate that
Allison does not acknowledge where the technology came from with its
roots in the Detroit Transmission Division and World War Two tanks.
The Legacy of the Assistant Driver in
American tanks: All tanks during WWII had an assistant driver,
who had the important task of watching where the tank or tank destroyer
was going while the driver was distracted while shifting gears and
double clutching. This was the case for the M3, M4, M10, and M36,
but not for the tanks and tank destroyers with either Hydra-Matic or
Torqmatic automatic transmission supplied by Detroit Transmission.
In these vehicles the assistant driver no longer needed to watch the
road because with the gears shifting automatically, and no clutch, the
driver could now focus on the road ahead. However, Army Ordnance
tank designers did not realize this until after WWII, when the M41
Walker Bulldog and the M48 Patton tanks and finally eliminated the
This World War Two Hydra-Matic 250-T Transmission can be seen at the Ropkey
Armor Museum in Crawfordsville, IN. The transmission is attached
to a Cadillac V-8 and would have seen applications in the M5 series
tanks, M8 motor gun carriages, and the LVT(3).
Note that not only does it say Hydra-Matic on the case, it also says
Detroit Transmission Division on it. One person on the internet
stated irrevocably in an email chain that Detroit Transmission never
existed. Just another case of someone thinking they were an expert
on something about which they know nothing. Author's photo.
This photo shows Cadillac a V-8 attached to the Hydra-Matic transmission. Author's photo.
Two Detroit Transmission Hydra-Matics each were used in M5 Stuart tanks
like this one seen at the 2013 Thunder over Michigan Airshow.
This photo shows a Detroit Transmission
Hydra-Matic transmission being installed along with the Cadillac V-8 into an M5 Stuart tank.
Photo added 2-19-2015.
This M24 Chaffee tank seen at
Ropkey Armor Museum also has two 250-T Hydra-Matics in it. Author's
Here can be seen rows of Detroit Transmission Hydra-Matics mated to GMC
270 cubic inch engines that are awaiting installation into Chevrolet
Staghound armored cars. Photo courtesy of the Military History
Institute in Carlisle, PA.
This Staghound (T17E1) with two Hydra-Matic
transmissions was photographed at the GM Milford Proving Grounds in June
The Hydra-Matic transmission was also used
in (410) Mark 1 armored snowmobiles built by Bombardier of Canada.
Three hundred and ninety six of the Mark 1s went to Great Britain with a
few of them making it to the Italian Campaign. Three of them went
to Russia. Photo added 1-19-2016.
This rare photo of the Mark 1 Armored
Snowmobile is one of the three that ended up with the Russian Army.
The photo shows the normal armament of a Bren Gun which could be mounted
on the side as shown here or in the front. Photo added 1-19-2016.
Borg-Warner built 5,924 LVT(3)s like this one seen at the National
Military History Center in Auburn, IN. Each one had two Detroit
Transmission Hydra-Matics in it. Author's photo.
Looking into the landing craft from the rear
ramp area one can see the engine and transmission covers have been
removed on each side. Author's photo.
This photo shows the Hydra-Matic
transmission connected to the Cadillac V-8 on the right or starboard
side of the LVT(3). Author's photo.
Here one can actually see the
Hydramatic embossed in the casting. Author's photo.
The left or port side
engine/transmission bay. Author's photo.
The Hydra-Matic on the port side had a
coating of dirt and oil on it. Author's photo.
This T18E2 GMC built Boarhound used two
Hydra-Matic transmissions and was photographed at the GM Proving Grounds
on January 19, 1943.
The 46 ton M26 Pershing was the second and
final application for the Torqmatic as produced during WWII by the Detroit
Transmission Division of GM. The M26 was the first "modern" tank
from which all future American tanks would take their design cues from.
A low profile, adequate armor and main gun, torsion bar suspension, rear
drive, and an automatic transmission made this the first modern American
tank. Author's photo taken
at Fort Jackson, SC.
The M-26 Pershing Torqmatic transmission had
three forward speeds and one reverse. First gear was a 1:1 ratio,
second gear 1:2.337 ratio and third gear 1:4.105 ratio. When in
first the M26 had a speed of 0-9mph, in second 6-19mph and in third its
speed range was 12-20 mph. The reverse ratio was 1:1.322 with
speed of 0-9mph. Photo from "TM
9-1735A Ordnance Maintenance--Medium Tanks M26 and M45, Power Train".
The M45 was the 105mm Howitzer version. Chrysler built 185 of the
M45s late in WWII.
The next two pages are from my page "One
Million Browning Machine Guns" located on the main GM page. Note
above that Detroit Transmission is listed as one of four GM divisions
that manufactured some of the 270 parts that went into a .50 cal Browning and 159 parts
that made up the .30 cal Browning machine gun. Photo added
Detroit Transmission manufactured parts went
to the weapons shown above. Photo added 2-19-2015.
Teamwork in Peace and War
This 1944 publication tells the
story of the early history of the Hydra-Matic Transmission as developed
for use on 1940 Oldsmobiles and 1941 Cadillacs, the Hydra-Matics
introduction to the M5 Stuart Tank, and the Torqmatic transmission's
development for the M18 Hellcat Tank Destroyer.
This gives an excellent insight into how the
Hydra-Matic and Torqmatic transmissions were introduced into World War
Two combat vehicles.
This page and the next two pages describe
the first time a tank was driven with an automatic transmission and its
advantages over a manual transmission.
The next four pages describe how the
Hydra-Matic transmission along with the Cadillac V-8 engine were mated
together in the M5 Stuart light tank.
This page describes the successful 560 mile
road trip the first M5 tank equipped with a Hydra-Matic transmission
made between Detroit, MI and Aberdeen, MD and how well it perfomed.
This page tells how the name "Hydra-Matic"
came into being.
The next four pages describe how Hydra-Matic
transmissions were developed for use in he M5.
The next five pages describe how Detroit
Transmission tooled up to produce the 250-T Hydra-Matic Transmission for
World War Two.
These two pages describe the Torqmatic
transmission as built by the Detroit Transmission Division.
On June 22, 1944 the Detroit Transmission
Division was awarded the prestigious Army-Navy "E" for Excellence Award.
900-T Hellcat Transmission